循环吸气支气管内瞬态气流运动特性的仿真研究

Simulation Study on Characteristics of the Transient Airflow Movement in Human Airways at Cyclic Inhalation Flow

人体支气管内的瞬态气流运动对气溶胶在支气管内的沉积产生重要影响,深入认识支气管内的瞬态气流运动特性,对于分析气溶胶在人体支气管内的沉积模式具有重要作用。应用计算流体动力学方法,对人体轻度运动强度下Weibel模型的3级到6级支气管内的瞬态气流运动特性进行了数值仿真,讨论了支气管对称平面、横截面内的瞬态气流组织形式。研究结果表明:在支气管的对称平面内,支气管分叉处产生气流分离现象;在吸气加速阶段,在3级支气管横截面内,没有产生涡流运动;在吸气加速阶段,4级支气管内,呈现出具有内壁附近区域速度高、外壁区域附近速度低的倾斜的抛物线特点的速度分布形式;5级支气管内,形成由两个涡流到四个涡流又到两个涡流的涡流演变过程。在6级支气管横截面内,在吸气加速阶段,和4级支气管横截面相似,在对称平面上下形成两个对称旋转的涡流运动,两个涡流中心分别处于上下平面的中心位置。

The transient airflow movement has tremendous effects on aerosol deposition in human airways. The understanding of the characteristics of the transient airflow movement in human airways plays a very important role in analyzing the aerosol deposition patterns. Computational fluid dynamics （CFD） was used to simulate the transient airflow movement in generations G3-G6 of Weibel model under light activity conditions, the transient airflow patterns in the middle plane and cross sections of the airways were discussed. The results showed that the phenomenon of airflow separation appeared at the divider in the middle plane of the bifurcation. In G3 the swirls didn＇ t generated during the accelerating inhalation. The velocity profiles displayed skewed parabolic for the high velocity （around inner wall and low velocity around outer wall in CA during the accelerating inhalation. In G5 the development process of swirls was with the characteristics of two swirls-four swirls-two swirls. Like the swirls in G4, two symmetry swirls appeared around the middle plane of the cress section and the center of the swirls located around the center of the middle plane of the cross section in G6 during the accelerating inhalation